Human Microbiome Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland.
Institute for Molecular Medicine Finland (FIMM), University of Helsinki, Helsinki, Finland.
NPJ Biofilms Microbiomes. 2022 Jun 29;8(1):50. doi: 10.1038/s41522-022-00312-0.
Bifidobacterium spp. are abundant gut commensals, especially in breast-fed infants. Bifidobacteria are associated with many health-promoting effects including maintenance of epithelial barrier and integrity as well as immunomodulation. However, the protective mechanisms of bifidobacteria on intestinal epithelium at molecular level are poorly understood. In this study, we developed a high-throughput in vitro screening assay to explore binding receptors of intestinal epithelial cells for Bifidobacterium bifidum. Short interfering RNAs (siRNA) were used to silence expression of each gene in the Caco-2 cell line one by one. The screen yielded four cell surface proteins, SERPINB3, LGICZ1, PKD1 and PAQR6, which were identified as potential receptors as the siRNA knock-down of their expression decreased adhesion of B. bifidum to the cell line repeatedly during the three rounds of siRNA screening. Furthermore, blocking of these host cell proteins by specific antibodies decreased the binding of B. bifidum significantly to Caco-2 and HT29 cell lines. All these molecules are located on the surface of epithelial cells and three out of four, SERPINB3, PKD1 and PAQR6, are involved in the regulation of cellular processes related to proliferation, differentiation and apoptosis as well as inflammation and immunity. Our results provide leads to the first steps in the mechanistic cascade of B. bifidum-host interactions leading to regulatory effects in the epithelium and may partly explain how this commensal bacterium is able to promote intestinal homeostasis.
双歧杆菌是丰富的肠道共生菌，尤其存在于母乳喂养的婴儿体内。双歧杆菌与许多促进健康的作用相关，包括维持上皮屏障和完整性以及免疫调节。然而，双歧杆菌在分子水平上对肠道上皮的保护机制还知之甚少。在本研究中，我们开发了一种高通量的体外筛选试验，以探索肠道上皮细胞与双歧杆菌结合的受体。通过逐个沉默 Caco-2 细胞系中的每个基因的小干扰 RNA (siRNA)，进行筛选。该筛选产生了四个细胞表面蛋白，即 SERPINB3、LGICZ1、PKD1 和 PAQR6，它们被鉴定为潜在的受体，因为其表达的 siRNA 敲低在三个轮次的 siRNA 筛选过程中反复降低了双歧杆菌与细胞系的黏附。此外，这些宿主细胞蛋白的特异性抗体阻断显著降低了双歧杆菌与 Caco-2 和 HT29 细胞系的结合。所有这些分子都位于上皮细胞的表面，其中四个中的三个，即 SERPINB3、PKD1 和 PAQR6，参与与增殖、分化和凋亡以及炎症和免疫相关的细胞过程的调节。我们的结果为双歧杆菌-宿主相互作用的机制级联反应的第一步提供了线索，这些反应导致在上皮细胞中产生调节作用，并部分解释了这种共生菌如何能够促进肠道内稳态。
